Chemical Energy Input Research Articles

Design, fabrication and characterization of a low-temperature co-fired ceramic gaseous bi-propellant microthruster

A gaseous bi-propellant chemical microthruster was developed using low-temperature co-fired ceramic (LTCC) tapes. A sapphire window and silver spark ignition electrodes were successfully co-fired in the LTCC microthruster. Thrust outputs between 0.2 mN and 1.97 mN could be achieved from the 9.9 mm3 thrust chamber by hot-gas operation using ethylene–argon/oxygen mixtures. A non-premixed combustion scheme was utilized by applying an inlet configuration with offset opposing fuel and oxidizer ports. The inlet port design was able to facilitate the generation of swirling flow. Fuel/oxidant mixing could be enhanced in the thrust chamber with the swirling streams according to the cold-flow multi-species 3D computational fluid dynamics (CFD) analysis. Flame chemiluminescence measurements through the transparent observation window were performed to characterize the flame structure in the miniature combustion chamber. The flame zone was found to coincide with the stoichiometric plane predicted by the CFD simulations. Thrust measurements were accomplished by measuring the impingement force of the exhaust jet on a precision balance. The disturbance introduced by the tubing and wiring on the continuous flow microthruster could therefore be eliminated. Thrust was linearly proportional to the total mass flow rate of the inlet. The chemical energy input of the microthruster was approximately 37 W for the maximal measured thrust of 1.97 mN.

Open system approaches in deterministic models of the emergence of homochirality

Three different general strategies are proposed for kinetic models of the emergence of homochirality in open systems: flow-through reactors, photochemical energy input, and chemical energy input from a sacrificial reagent. Using a simple, second-order chiral autocatalytic core model, it is shown that all these scenarios lead to similar mathematical description despite the fundamentally different chemical background and practically complete homochirality is reached in all of these cases. It is also argued that the photochemical energy input scenario might not be compatible with a sunlight-driven natural process.

PR65, the HEAT-repeat scaffold of phosphatase PP2A, is an elastic connector that links force and catalysis

PR65 is the two-layered (alpha-alpha solenoid) HEAT-repeat (Huntingtin, elongation factor 3, a subunit of protein phosphatase 2A, PI3 kinase target of rapamycin 1) scaffold of protein phosphatase PP2A. Molecular dynamics simulations predict that, at forces expected in living systems, PR65 undergoes (visco-)elastic deformations in response to pulling/pushing on its ends. At lower forces, smooth global flexural and torsional changes occur via even redistribution of stress along the hydrophobic core of the molecule. At intermediate forces, helix-helix separation along one layer ("fracturing") leads to global relaxation plus loss of contact in the other layer to unstack the affected units. Fracture sites are determined by unusual sequences in contiguous interhelix turns. Normal mode analysis of the heterotrimeric PP2A enzyme reveals that its ambient conformational fluctuations are dominated by elastic deformations of PR65, which introduce a mechanical linkage between the separately bound regulatory and catalytic subunits. PR65-dominated fluctuations of PP2A have the effect of opening and closing the enzyme's substrate binding/catalysis interface, as well as altering the positions of certain catalytic residues. These results suggest that substrate binding/catalysis are sensitive to mechanical force. Force could be imposed from the outside (e.g., in PP2A's response to spindle tension) or arise spontaneously (e.g., in PP2A's interaction with unstructured proteins such as Tau, a microtubule-associated Alzheimer's-implicated protein). The presented example supports the view that conformation and function of protein complexes can be modulated by mechanical energy inputs, as well as by chemical energy inputs from ligand binding. Given that helical-repeat proteins are involved in many cellular processes, the findings also encourage the view that mechanical forces may be of widespread importance.

Assembly and Simple Demonstration of a Micropump Installing PDMS-Based Thin Membranes as Flexible Micro Check Valves

Integration of chemical or biochemical systems creates extremely efficient devices exploiting the advantages of microspaces. Recently, various microfluidic devices have been developed to make micro chemical processes more sophisticated. On the other hand, we demonstrated the concept of a cardiomyocyte pump using only chemical energy input to cells as a driver (Tanaka et al. Lab Chip 6(3), pp. 362-368). However, its flow rate was too poor to be applied for practical applications of micro chemical systems mainly because of the inefficiency of the check valves made of polyimide. As cardiomyocytes' force is weak, more flexible materials must be used. In this report, a more flexible material, poly(dimethylsiloxane) (PDMS) check valves were designed and fabricated, and then, the check valve function was demonstrated by pumping fluid in an assembled micropump incorporating the PDMS check valves. Water was dropped on an inlet of the microchannel, and a diaphragm of the micropump was oscillated using a pair of tweezers to prove the function of the valves. From the result, pumping volume per stroke was calculated as 1.7 micro/stroke. The developed valves are not only usable for our cardiomyocyte pumps but also applicable to general micro and nano fluidic devices for biomedical fields such as immune assay systems owning to easy and inexpensive fabrication method of the valves.

RNA polymerase motors: dwell time distribution, velocity and dynamical phases

Polymerization of RNA from a template DNA is carried out by a molecular machine calledRNA polymerase (RNAP). It also uses the template as a track on which it moves as amotor, utilizing chemical energy input. The time it spends at each successive monomer ofDNA is random; we derive the exact distribution of these ‘dwell times’ in our model. Theinverse of the mean dwell time satisfies a Michaelis–Menten-like equation and is alsoconsistent with a general formula derived earlier by Fisher and Kolomeisky for molecularmotors with unbranched mechano-chemical cycles. Often many RNAP motors movesimultaneously on the same track. Incorporating the steric interactions among the RNAPsin our model, we also plot the three-dimensional phase diagram of our model for RNAPtraffic using an extremum current hypothesis.

Energy efficiency and the influence of gas burners to the energy related carbon dioxide emissions of electric arc furnaces in steel industry

Abstract Determining the complete energy balance of an electric arc furnace (EAF) provides an appropriate method to examine energy efficiency and identify energy saving potentials. However, the EAF energy balance is complex due to the combined input of electrical energy and chemical energy resulting from natural gas (NG) combustion and oxidation reactions in the steel melt. In addition, furnace off-gas measurements and slag analysis are necessary to reliably determine energy sinks. In this paper 70 energy balances and energy efficiencies from multiple EAFs are presented, including data calculated from plant measurements and compiled from the literature. Potential errors that can be incorporated in these calculations are also highlighted. The total energy requirement of these modern EAFs analysed ranged from 510 to 880 kWh/t, with energy efficiency values (η = ΔHSteel/ETotal) of between 40% and 75%. Furthermore, the focus was placed on the total energy related CO2 emissions of EAF processes comprising NG combustion and electrical energy input. By assessing multiple EAF energy balances, a significant correlation between the total energy requirement and energy related specific CO2 emissions was not evident. Whilst the specific consumption of NG in the EAF only had a minor impact on the EAF energy efficiency, it decreased the specific electrical energy requirement and increased EAF productivity where transformer power was restricted. The analysis also demonstrated that complementing and substituting electrical energy with NG was beneficial in reducing the total energy related CO2 emissions when a certain level of substitution efficiency was achieved. Therefore, the appropriate use of NG burners in modern EAFs can result in an increased EAF energy intensity, whilst the total energy related CO2 emissions remain constant or are even decreased.

Structure and Mechanism of Protein Stability Sensors: Chaperone Activity of Small Heat Shock Proteins

Small heat shock proteins (sHSP) make up a remarkably diverse group of molecular chaperones possessing a degree of structural plasticity unparalleled in other protein superfamilies. In the absence of chemical energy input, these stability sensors can sensitively recognize and bind destabilized proteins, even in the absence of gross misfolding. Cellular conditions regulate affinity toward client proteins, allowing tightly controlled switching and tuning of sHSP chaperone capacity. Perturbations of this regulation, through chemical modification or mutation, directly lead to a variety of disease states. This review explores the structural basis of sHSP oligomeric flexibility and the corresponding functional consequences in the context of a model describing sHSP activity with a set of three coupled thermodynamic equilibria. As current research illuminates many novel physiological roles for sHSP outside of their traditional duties as molecular chaperones, such a conceptual framework provides a sound foundation for describing these emerging functions in physiological and pathological processes.

Interacting RNA polymerase motors on a DNA track: Effects of traffic congestion and intrinsic noise on RNA synthesis

RNA polymerase (RNAP) is an enzyme that synthesizes a messenger RNA (mRNA) strand which is complementary to a single-stranded DNA template. From the perspective of physicists, an RNAP is a molecular motor that utilizes chemical energy input to move along the track formed by DNA. In many circumstances, which are described in this paper, a large number of RNAPs move simultaneously along the same track; we refer to such collective movements of the RNAPs as RNAP traffic. Here we develop a theoretical model for RNAP traffic by incorporating the steric interactions between RNAPs as well as the mechanochemical cycle of individual RNAPs during the elongation of the mRNA. By a combination of analytical and numerical techniques, we calculate the rates of mRNA synthesis and the average density profile of the RNAPs on the DNA track. We also introduce, and compute, two different measures of fluctuations in the synthesis of RNA. Analyzing these fluctuations, we show how the level of intrinsic noise in mRNA synthesis depends on the concentrations of the RNAPs as well as on those of some of the reactants and the products of the enzymatic reactions catalyzed by RNAP. We suggest appropriate experimental systems and techniques for testing our theoretical predictions.

Can microbial growth yield be estimated using simple thermodynamic analogies to technical processes?

In view of the prime importance of the biomass yield in microbial growth for research, for environmental and for industrial applications some thermodynamic concepts are reviewed that were developed over the years in order to understand the large variations observed in this parameter and to predict it. Special emphasis is given to a comparison between cellular growth and an energy transducer, which uses an input of chemical or mechanical energy to drive a useful output reaction. It turns out that it is impossible to calculate energetic efficiencies and to predict biomass yield based on correlations of the latter because the very concept is plagued with internal inconsistencies. Nevertheless, the energy transducer model reflects at least qualitatively the compromise between two extreme types of metabolism that must have emerged during evolution. On one hand, one can imagine that microbial metabolism could dissipate most of the Gibbs energy contained in the substrates for generating large driving forces and thus fast metabolism, but this would result in small biomass yields. On the other hand, metabolism could maximize biomass yield but this would minimize the chemical driving forces and thus the growth rate. It appears that a certain range of values of Gibbs energy dissipation somewhere between these two extremes may have emerged during evolution. Correlations for estimating this range of Gibbs energy dissipation for specific microbial growth system have been developed. Based on a Gibbs energy balance, the wide variety of growth yields occurring in nature may be explained and roughly predicted.

A micro-spherical heart pump powered by cultured cardiomyocytes

Miniaturization of chemical or biochemical systems creates extremely efficient devices exploiting the advantages of microspaces. Although they are often targeted for implanted tissue engineered organs or drug-delivery devices because of their highly integrated systems, microfluidic devices are usually powered by external energy sources and therefore difficult to be used in vivo. A microfluidic device powered without the need for external energy sources or stimuli is needed. Previously, we demonstrated the concept of a cardiomyocyte pump using only chemical energy input to cells as a driver (Yo Tanaka, Keisuke Morishima, Tatsuya Shimizu, Akihiko Kikuchi, Masayuki Yamato, Teruo Okano and Takehiko Kitamori, Lab Chip, 6(3), pp. 362-368). However, the structure of this prototype pump described there included complicated mechanical components and fabricated compartments. Here, we have created a micro-spherical heart-like pump powered by spontaneously contracting cardiomyocyte sheets driven without a need for external energy sources or coupled stimuli. This device was fabricated by wrapping a beating cardiomyocyte sheet exhibiting large contractile forces around a fabricated hollow elastomeric sphere (5 mm diameter, 250 microm polymer thickness) fixed with inlet and outlet ports. Fluid oscillations in a capillary connected to the hollow sphere induced by the synchronously pulsating cardiomyocyte sheet were confirmed, and the device continually worked for at least 5 days in this system. This bio/artificial hybrid fluidic pump device is innovative not only because it is driven by cells using only chemical energy input, but also because the design is an optimum structure (sphere). We anticipate that this device might be applied for various purposes including a bio-actuator for medical implant devices that relies on biochemical energy, not electrical interfacing.

Advanced EAF oxygen usage at Vallourec-Mannesmann Saint-Saulve steelworks

Oxygen usage has played a crucial role in the ongoing EAF process improvement and has enabled furnace operators to optimize the chemical energy input, reaching unprecedented efficiencies and productivity. This article will present the fundamental principles governing the design of an optimized chemical energy system through scrap oxy-cutting and melting, decarburisation, post-combustion and slag foaming. It will be illustrated with industrial results obtained at the Vallourec Mannesmann Saint-Saulve site, where a PyreJetTM and ALARCTM PC system, using the newly designed DRAGON Panel, has been recently commissioned.

Early star formation, nucleosynthesis and chemical evolution in proto-galactic clouds

We present numerical simulations to describe the nucleosynthesis and evolution of pre-galactic clouds in a model which is motivated by cold dark-matter simulations of hierarchical galaxy formation. We adopt a SN-induced star-formation mechanism within a model that follows the evolution of chemical enrichment and energy input to the clouds by Type II and Type Ia supernovae. We utilize metallicity-dependent yields for all elements at all times and include effects of finite stellar lifetimes. We derive the metallicity distribution functions for stars in the clouds, their age-metallicity relation and relative elemental abundances for a number of alpha- and Fe-group elements. The stability of these clouds against destruction is discussed, and results are compared for different initial mass functions. We find that the dispersion of the metallicity distribution function observed in the outer halo is naturally reproduced by contributions from many clouds with different initial conditions. The scatter in metallicity as a function of age for these stars is very large, implying that no age-metallicity relation exists in the early stages of galaxy formation. Clouds with initial masses ≳ presently observed globular clusters are found to survive the first 0.1 Gyr from the onset of star formation, suggesting that such systems may have contributed to the formation of the first stars and could have been self-enriched. More massive clouds are only stable when one assumes an initial mass function that is not biased towards massive stars, indicating that even if the first stars were formed according to a top-heavy mass function, subsequent star formation was likely to have proceeded with a present-day mass function or happened in an episodic manner. The predicted relative abundances of some alpha- and Fe-group elements show good agreement with the observed values down to metallicities below [Fe/H] ∼−4 when the iron yields are reduced relative to stellar models. The observed scatter is also reproduced for most elements including the observed bifurcation in [α/Fe] for stars with low [Fe/H]. However, the predicted dispersion may be too large for some elements (particularly alpha elements) unless a limited range of progenitor masses contributing to the abundances of these elements is assumed. The contributions to the abundances from supernovae with different progenitor masses and metallicity are discussed. The results suggest that the low-mass end of SNeII was probably absent at the very lowest metallicities and that the upper mass limit for the first stars that contributed to nucleosynthesis may be ≲40 M⊙.

Advanced EAF oxygen usage at Saint-Saulve steelworks

Tailored oxygen use has played a crucial role in EAF process improvement, enabling furnace operators to optimise chemical energy input, to achieve high efficiency and productivity. The fundamentals underlying an optimised chemical energy system, involving scrap oxycutting and melting, decarburisation, post-combustion and slag foaming, are described. This strategy is illustrated with industrial results obtained at the Vallourec and Mannesmann Saint-Saulve site, where a PyreJet and Alarc PC system, using the newly designed Dragon panel, has been recently commissioned.

Development of a microreactor as a thermal source for microelectromechanical systems power generation

An alumina ceramic 12.5×12.5×5.0 mm microreactor was constructed using a modified stereolith-ography process. The design was based on a “Swiss roll” concept of double spiral-shaped channels to facilitate a high level of heat transfer between the reactants and combustion products and wall surface contact of the flow through the microreactor body. Self-sustained combustion of hydrogen and air mixtures was demonstrated over a wide range of fuel/air mixtures and flow rates for equivalence ratios from 0.2 to 1.0 and chemical energy inputs from 2 to 16 W. Depositing platinum on gamma alumina on the internal walls enabled catalytic ignition at or near room temperature and self-sustained operation at temperatures to 300°C. Catalyst degradation was observed at higher operating temperatures and reignition capabilities were lost. However, sustained operation coul be obtained at wall temperatures in excess of 300 °C. apparently stabilized by a combination of surface and gas-phase reaction phenomena. A global energy balance model was developed to analyze overall reactor performance characteristics. The reactor design and operating temperature range have potential applications as a heat source for thermoelectric and pyroelectric power generation at small scales compatible with microelectromechanical systems applications.

Effect of electrical/chemical energy input on the Interior Ballistics of an Electrothermal Chemical Gun

AbstractRecent studies have clearly indicated that an electothermal chemical (ETC) gun provides many advantages over solid and liquid propellant guns. However, the interior ballistic process of an ETC gun has not yet been fully investigated. Specifically, the effects of the energy ratio between the electrical and chemical energy input on gun performance is not well understood. Nor is it known exactly how chemical energy is converted to propulsive energy during the ETC gun event. In view of this, a comprehensive theoretical model taking into full account electrical/chemical energy input, liquid entrainment process, distribution of dispersed droplets, and liquid propellant combustion, is developed to simulate the interior ballistics of an ETC gun. Governing equations are formulated from first principles for five different regions, including the gas phase (i.e., Taylor cavity), working fluid (i.e., liquid propellant), dispersed droplets, projectile, and plasma generation cartridge (PGC). Various energy ratios with two different PFN discharge characteristics are employed to evaluate ETC gun performance. Results indicate that the gun champer pressure, muzzle velocity, and ballistic efficiency depend strongly on the energy ratio. The electrical energy input and chemical energy release processes show unequal influence on the gun performance over different stages of ETC gun event. The predicted time history of the breech presure is compared with the measured breech pressur available in the literature. The results show that shapes of the breech pressure‐time traces and values of the peak pressure predicted by the present model agree reasonably well with the experimental data.

Total emission of soot and thermal radiation by free turbulent diffusion flames

The emission of soot and thermal radiation by free turbulent diffusion flames of CO, H 2, CH 4, C 2H 6, C 3H 8, C 2H 4, and C 2H 2 was studied over a range spanning the transition from forced convection to natural convection (burner diameters 0.7–10.9 mm, buoyancy Richardson ratios Ri L ≡ π g ϱ ∞L 3 4 G ̇ 0 of 2–10,000, where L is flame length, G ̇ 0 is source momentum flux, ϱ ∞ is ambient air density, and g is acceleration due to gravity. Both soot emission, expressed as the ratio χ S between soot output and carbon input, and radiant cooling, expressed as the ratio χ R between radiant heat loss and chemical energy input (heat of combustion), rise with Ri L and tend to plateaus as natural convection becomes dominant Ri L > 2000). However, it also appears that they fundamentally depend on parameters other than Ri L, χ S being strongly correlated with the second Damkohler ratio or chemical loading factor and χ R with the analogous thermal loading factors. The behavior observed is in reasonable accord with theoretical expectations. The plateau values of χ R at high Ri L are 0.18–0.4 for the hydrocarbon fuels, and for χ S they are 0.0015–0.0045 for the hydrocarbons other than acetylene. Acetylene flames emit up to 100 times as much soot as the others. Buoyancy is unimportant below Ri L = 200 since χ S and χ R are then independent of burner orientation (vertical or horizontal). Also, the soot emission for hydrocarbon fuels other than acetylene seems to stablize, indicating χ S ⋍ 0.0003 at Ri L < 200.

The effects of orientation and crystallinity on the solvent‐induced crystallization of poly(ethylene terephthalate). I. Sorption‐ and diffusion‐related phenomena

AbstractThis series of reports summarizes the results of an experimental research program designed to establish the effects of preexisting orientation and crystallinity on solvent‐induced crystallization of poly(ethylene terephthalate) films. Dimethylformamide was used as a model for a strongly interacting solvent. Special emphasis has been given to the kinetics of crystallization and diffusion, the morphological and structural modifications, and the accompanying changes in physical properties. This article deals with solvent sorption and desorption. Solvent diffusion and the extent of crystallization decreased with increasing orientation and crystallinity in the starting films, with crystallinity being more important. Despite the semicrystalline morphology, the overall diffusion behavior was found to be Fickian, allowing the calculation of pseudodiffusion coefficients which were dependent on both the draw ratio and the treatment temperature. Solvent treatments at elevated temperatures involved a dual input of thermal and chemical energy, which caused the films to behave differently above and below the glass transition temperature. Solvent desorption and reversible swelling were also found to be dependent on preexisting structure and treatment conditions.